The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
legwh-
DEFINITION:
Light, having little weight. Derivatives include levity, carnival, elevate, leprechaun, and lung. 1. Suffixed form *legwh-t-.a.light2, from Old English lht,loht, light; b.lighter2, from Old English lhtan, to lighten. Both a and b from Germanic *lht(j)az.2. Suffixed form *legwh-wi-.leaven, lever, levity; alleviate, carnival, elevate, legerdemain, mezzo-relievo, relevant, relieve, from Latin levis, light, with its derivative levre, to lighten, raise. 3. Variant form *lagwh-.leprechaun, from Old Irish l-, small. 4. Nasalized form *l(e)ngwh-.lung, from Old English lungen, lungs (from their lightness), from Germanic *lung-.5. Latin oblvsc, to forget, attributed by some to this root, is more likely from lei-. (Pokorny legh- 660.)
ht, l
oht, light; b. lighter2, from Old English l
re, to lighten, raise. 3. Variant form *lagwh-. leprechaun, from Old Irish l
-, small. 4. Nasalized form *l(e)ngwh-. lung, from Old English lungen, lungs (from their lightness), from Germanic *lung-. 5. Latin obl
h- 660.) 
